User Manual

PMP 450 Planning Guide Data network planning
pmp-0047 (December 2012)
2-47
Special case VLAN numbers
This system handles special case VLAN numbers according to IEEE specifications:
Table 21 Special case VLAN IDs
VLAN
Number
Purpose Usage Constraint
0
These packets have 802.1p priority, but are otherwise handled
as untagged.
Should not be used as a
management VLAN.
1
Although not noted as special case by IEEE specifications,
these packets identify traffic that was untagged upon ingress
into the SM and should remain untagged upon egress. This
policy is hard-coded in the AP.
Should not be used for system
VLAN traffic.
4095 This VLAN is reserved for internal use. Should not be used at all.
SM membership in VLANs
With the supported VLAN functionality, the radios determine bridge forwarding on the basis of not only the
destination MAC address, but also the VLAN ID of the destination. This provides flexibility in how SMs are used:
• Each SM can be a member in its own VLAN.
• Each SM can be in its own broadcast domain, such that only the radios that are members of the VLAN can see
broadcast and multicast traffic to and from the SM.
• The network operator can define a work group of SMs, regardless of the AP(s) to which they register.
PMP modules provide the VLAN frame filters that are described in Table 22.
Table 22 VLAN filters in point-to-multipoint modules
Where VLAN is
active,
if this parameter
value is selected …
then a frame is discarded if…
because of this VLAN
filter in the software:
entering the bridge/
NAT switch through…
Ethernet… TCP/IP…
any combination of VLAN
parameter settings
with a VID not in
the
membership table
Ingress
any combination of VLAN
parameter settings
with a VID not in the
membership table
Local Ingress
Allow Frame Types:
Tagged Frames Only
with no 802.1Q tag
Only Tagged
Allow Frame Types:
Untagged Frames Only
with an 802.1Q tag,
regardless of VID
Only Untagged